EUV Membrane Doping and Cap Layers for Thermal Management
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Solution Overview
Problem
EUV membranes in lithographic apparatuses face challenges with temperature management, as they absorb residual EUV radiation, leading to increased temperatures and potential damage, especially when used with high-power EUV sources, and existing solutions do not effectively manage thermal gradients or IR radiation emission.
Innovation Solution
The EUV membranes are doped with impurities or coated with a metal cap layer to enhance IR emissivity, allowing for improved thermal management by increasing the membrane's ability to radiate heat while maintaining high EUV transmission, using materials like polysilicon, Si3N4, and metals such as Ru to achieve semi-metallic behavior and reduce temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If EUV membranes are made extremely thin to minimize EUV radiation absorption, then EUV transmission is improved, but the membrane becomes more susceptible to temperature damage and breakage
Solution Approach 1:
The patent applies composite materials by combining multiple protective layers (cap layers) made of different materials (e.g., silicon nitride, silicon oxide, boron nitride) with the core EUV membrane material (polysilicon). This composite structure provides both high EUV transmission and enhanced mechanical strength and thermal stability, resolving the contradiction between thinness for transmission and durability for reliability.
Solution Approach 2:
The patent implements beforehand cushioning by adding protective cap layers on both sides of the EUV membrane before exposure to harsh conditions. These cap layers act as a buffer against thermal stress, mechanical stress, and chemical etching, allowing the thin membrane to maintain both high transmission and reliability under operational conditions.
2Productivity
If EUV membranes are exposed to high-power EUV radiation sources, then productivity is improved, but temperature increase leads to membrane damage
Solution Approach 1:
The patent uses protective cap layers as intermediary elements between the high-power EUV radiation source and the core membrane. These cap layers absorb and distribute thermal energy, acting as a thermal buffer that allows high-power operation for improved productivity while protecting the membrane from excessive temperature increases.
Solution Approach 2:
The patent changes the thermal and mechanical parameters of the membrane system by introducing cap layers with specific thermal conductivity, heat capacity, and mechanical strength properties. This parameter modification enables the system to withstand high-power EUV radiation while maintaining membrane integrity, thus allowing higher productivity without proportional temperature damage.
3Reliability
If protective cap layers are added to prevent EUV-induced plasma etching, then reliability is improved, but EUV transmission is reduced
Solution Approach 1:
The patent applies local quality by making the cap layers thin (e.g., 1-10 nm) and positioning them only on the surfaces of the membrane where protection is needed. The core membrane remains thin and highly transparent. This localized protection approach maintains high EUV transmission through the bulk while providing sufficient surface protection against plasma etching.
Solution Approach 2:
The patent changes the thickness parameter of protective layers to an optimal range that balances protection and transmission. By controlling cap layer thickness to be sufficiently thin (nanometer scale), the system achieves both reliability improvement through protection and minimal impact on EUV transmission, resolving the contradiction between these two parameters.
4Temperature
If cooling mechanisms are added to manage thermal load, then temperature control is improved, but device complexity increases
Solution Approach 1:
The patent implements self-service thermal management where the protective cap layers and membrane structure themselves provide passive thermal management through their inherent thermal conductivity and heat capacity. The design allows the membrane system to self-regulate temperature to some extent without requiring active cooling mechanisms, thus improving temperature control while avoiding increased device complexity.
Solution Approach 2:
The patent replaces active mechanical cooling systems with passive thermal management through material selection and结构设计. By choosing materials with appropriate thermal properties and designing the layer structure to facilitate heat dissipation, the system achieves improved temperature control without the complexity of active cooling mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces temperature gradients and extends the lifetime of EUV membranes by enhancing IR emissivity, allowing them to handle higher EUV source powers without damage, while maintaining sufficient EUV transmission and mechanical strength.
Implementation Method 1
Because pellicles are in vacuum, the main process for pellicle cooling is radiative heat transfer
Implementation Method 2
EUV membranes may have a reduced infrared emissivity which may be improved by doping the EUV membrane with impurities
Data Source
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AI summary
Disclosed is a membrane transmissive to EUV radiation, which may be used as a pellicle or spectral filter in a lithographic apparatus. The membrane comprises one or more high doped regions wherein said membrane is doped with a dopant concentration greater than 1017 cm-3, and one or more regions with low (or no) doping. The membrane may have a main substrate having low doping and one or more additional layers, wherein said high doped regions are comprised within some or all of said additional layers.